The present invention relates to a device for de-agglomeration and electrostatic charging of a pulverized powder for inhalation by means of stationary or portable devices, whereby powder refers to active pharmaceutical substances and mixtures and specially treated preparations intended to be administered via the respiratory tract.
Administering of medical powders today is performed in numerous ways. Within health care more and more is focussed on the possibility of dosing powder directly to the lungs by means of an inhaler to obtain an effective, quick and patient-friendly administering.
For the medical powders, being administered by means of an inhaler, to land in the lungs, the powder should have a grain size of 1 to 6 xcexcm. A larger grain size will stick in the mouth and throat and a smaller grain size accompanies the expiration air.
Powder having a small grain size will have a strong tendency of agglomerating, i.e. to get conglomerated. In the inhalers. which are used today, a large extent of the active substance is in the form of agglomerates when it is dosed and much powder therefore will stick in the upper respiratory tract. Different ways to de-agglomerate the powder have been developed and in most cases the inhalation air is utilized for decomposing the agglomerates.
It is also common to use carriers having a larger grain size onto which the fine powder is distributed. Upon inspiration the large grains will then stick in the oral cavity while the small grains are set free and proceed to the lungs. Certain manufacturers also use electrically driven propellers, piezo-vibrators and/or mechanical vibration to decompose the agglomerates. Thus, achieving a very large portion of individual particles in the inspiratory air is a very important factor for obtaining a high degree of effectiveness upon inhalation.
As a complete de-agglomeration is difficult to achieve it is desirable that an additional separation stage is inserted in the form of a classification, which separates remaining agglomerates from the decomposed individual particles.
In the Swedish patent publication SE 504 458 a device for an inhaler is disclosed, which utilizes a rotating drum as dosing device together with an electric field, which document hereby is incorporated by reference.
The present invention discloses a method and a device for classification and, if required, electrostatic charging of a resulting fine powder especially intended for inhalation purposes. The electrostatic charging takes place by means of tribo-, corona- and/or induction-charging. Charging of the powder is from now on referring to an electrostatic charging according to any of the mentioned ways or a combination of those. Particularly the present invention is intended for use in dosing powder directly to the inspiratory air, alternatively providing a dosing device with electrostatically charged de-agglomerated powder for a more controlled dosing to the inspiratory air, alternatively application to a carrier for further preparation and introduction to an inhaler or other device, e.g., a piece of plaster or the like.
The classification preferably takes place in that the electrostatically charged powder is separated by a device decomposing a suitable substance, whereby the powder is given appropriate velocity. The powder is in this manner conveyed into an electric field, which preferably is perpendicular to the direction of the powder motion. By adapting the strength of the electric field decomposed powder, i.e. individual particles resembling dust, will by the electric field be attracted to a device from which dosing of individual particles takes place. The larger particles (the agglomerates) will proceed straight ahead in an original direction of motion as their kinetic energy is essentially larger than that for the small particles. In this manner an almost complete separation of individual particles from heavier agglomerated particles is obtained and a prerequisite for a very good dosing of the substance thereby will exist.
The device for accelerating the powder to an appropriate velocity is designed, according to different embodiments of the present invention, as a rotating brush flipping the powder, a vibrating membrane, a piezo-electric member or a fan. It is important to achieve an even and controllable acceleration of the powder, as the velocity should be adapted to the electric field and the distance to the reception device.
At the same time as the powder is accelerated, the powder preferably is electrostatically charged by selection of appropriate techniques and material. To obtain correct potential and correct sign of the potential an appropriate material must be selected and this takes place by considering how different materials are positioned in the tribo-electric series. The distance between two materials where tribo-charging takes place give rise to a possibility to control the potential strength intended to be achieved.
The process takes place in a classification device where releasing from a de-agglomeration zone takes place in a direction towards a reception device and where an electric field is arranged perpendicular to the direction of release. The kinetic energy, which is essentially larger for the heavier agglomerates, then swill carry the large particles to the reception device, while the small individual dust resembling particles will be made to attract a dosing drum by means of the electric field. In this way only the individual particles in practice will be utilized for dosing. A thin layer of electrostatically charged particles will thereby place themselves onto the rotatory dosing drum.
The dosing then takes place, for instance, by means of an attracting electrode having an appropriate voltage attracting the small powder grains from the dosing drum. An air-stream, the inspiratory air, will carry away the powder grains before they reach the attracting electrode. The amount of dosed powder can be governed by connecting and disconnecting the voltage. Alternatively, the dosing may be regulated by inserting an electronic filter between the dosing drum and the attracting electrode. A further alternative for governing the dosing is to vary the electric field in the classification device.
The invention is defined by the independent claims 1 and 3 and different embodiments are defined by the dependent claims 2-4 and 6-9.